Electric heater



April 9, 1935s L, P, HYNES LQQZMG ELECTRIC HEATER Filed Jan. 21, 1932' 2sheets-sheet 1l INVENTOR ATTORNEY L. P. HYNES ELECTRIC HEATER April 9,1935.

Filed Jam.A 21, 1932 2 Sheets-Sheet 2 E 91E lui, f 1

INVENTOR Bee I? Hynes ATTORNEY Patented Apr. e, 193s .Parlzzrlr lOFFICEELECTRIC HEATER Lee P. Hynes, Philadelphia, Pa. Application January 21,193%2, Serial No. 588,035

37 claims.

For a detailed description of the present form .of my invention,reference may be had to the vfollowing. specification and to theaccompanying drawings forming a part thereof, wherein Fig. l is a sideelevation of my exible heater;

Fig. 2 is an endl elevation of my insulator element;

Fig. 3 shows my exible' heater being introduced into a bent tube;

Fig. 4 shows one form of connection;

Figs. 5 and 6 show pipe joints;

Fig. 7 shows the application of my invention to -agateinadam;

Fig. 8 shows the suspension of a line of heaters by means of theiiexible strip;

Fig. 9 is a front elevation of the dam gate illustrated in Fig. 7.

My invention relates to an electric heater, including the coils, theinsulator and the insulation mounting, which is intended particularlyfor use in large installations, such, for instance, as the melting ofice from the guides of hydroelectric flood gates, or the prevention offreezing of water pipes in winter, or maintaining the ilow of heavyviscous liquids in pipes or maintaining a railway track free of ice. Insuch instances lines of metalpipe fty or one hundred feet long areequipped with heaters, and are handled in long water-tight sections,While, in other installations, great numbers of heaters areemployed,involving thousands of unit insulation sections, which. by my invention,are made capable of ready man pulation for construction, transportation,installationand repair. This is particularly true in cases where theoutside metal pipes are iirst placed in position and the heater linesinserted afterwards. This is true to a largedegree, even if theenclosing pipe is a ilexible hose, so long as the bends in the hose arenot sharp enouglrto prevent insertion of the wires. In the case' of toosharp bends the Wires may be inserted in the flexible hose before thehose is laid.. That will meet certainy situations, the flexible hosebeing water tight and closed at one end by suitable fittings, the otherend being open for insertion and connection of the wires. In allinstances the heater as a whole should be simple and capable of reliableoperation for long periods, without attention to repairs, and myherein-described heater itself has proved capable -of meeting all suchpractical requirements under diilicult conditions.

In particular my invention makes it possible to ship completely finishedapparatus from a factory, while, at the point oi application, requiresmere assembling, in ready, easy fashion, without (ci. zie-'19) furtherconstructive work on it remaining to be done on the ground.

Referring to the drawings., it will be observed that my heater is basedprimarily on a long flexible metal supporting strip'marked A. This stripA is not in the electric circuit, but is merely a mechanical support fora series of comparatively short insulating blocks or sections B.- Such asupport A provides for the upholding and manipulation of a long line ofinsulator blocks, many in number. This is particularly applicable to thetype of heaters to which my invention chiefly belongs, wherein it isimportant to construct and manipulate the heaters in long linesapplicable, for instance, to a long pipe and containing a great amountof heater-Wire distributed longitudinally along the pipe. It is ofspecial value in that it permits a line of insulators, with the wirestherein, to be suspended vertically in a pipe from its upper end. On theupper end of the said flexible strip a hook is formed by bending overthe strip and this hook is merely lodged over the end of the pipe andcarries the entire line of insulators. By this means also the number ofleading-in connections, which have to be insulated in the pipe andprotected outside of the pipe, is greatly reduced. Such leading-in wirescan thus be limited in most cases, to one end of the pipe, in contrastto a number of such leading-in wires applied at distant points along thelength of the pipe. Another advantage of the strip form of the supportis that it may be made ilexible without impairing its strength. Thestrip form of support can also be made quite thin and thereby addlittleto the cross section of the heater. 'It

also permits the insulator block to be comparatively short andslightlyyseparated, each fromthe one following it. By this means theseries of insulators as a whole may have the desired llexibility whilethe mechanical strength of the line of insulators is supplied by themetallic strip, rather than by the insulators themselves. At the presenttime the most available material for insulators, such as I use, is of aporcelain nature, which is fragile' and, unless of inordinate size, isweak, besides being hard and inflexible. v So a single piece ofporcelain as a support of such a length as I require in most cases,would not have suflicient strength, unless of impracticable size incross section, and wouldv not be bendable and also extremely liable tocracking and breakage. But by means of my supporting metallic strip andcomparatively short insulators 'spaced slightly apart, I secure, not

all the insulation that is required electrically,

with only small demands upon the mechanical qualities of the porcelain.

My short pieces of porcelain, marked individually B in the drawings, Iconstruct with a :dat base portion C having inclined sides (see'Fig. 2)and on the side opposite to' the metal strip is a separate rib Dextending longitudinally thereof. I then add to the block at intervalstransversely disposed, upwardly projecting, rounded flanges E. Theseanges or arches I perforate with concentricholes, see F, G and H in Fig.2. Through these holes I extend thel conducting wires K, preferably inthe form of a spiral coil. By running the coils K throughl the holes inthe porcelain iianges E, I avoid the need of fastening devices attachedat intervals to secure the` coil to the porcelains. Usually thisconductor, which is wound into'the coils, may be left bare of the usualinsulating covering since it is insulated on all sides and separatedfrom the interior walls of the nietal tube by the porcelain. The blocksD may be connected with the support A in any desired manner. However,for the purposes of illustration, said blocks are shown as provided withshouldered openings O leading downwardly therethrough from the tops ofthe-ribsj D to the bottoms of the-blocks. Suspended in said recesses aresplit metal members a Vhaving heads a' engaging the shoulders of saidopenings O, the free ends a2 being extended through suitable openings inthe support a, and spread apart as clearly shown in Figure 1.

`These insulator blocks are in cross sectionnearly circular, so thatwith the flexible ymetal strip they will substantially t into a roundtube. This also permits three holes in the projections, which allows aB-phase circuit to be carried thereby in safety It also brings the threeconductors nearthe center of the block and concentric therewith.

The heater, as above described, is ordinarily,

enclosed in a sealed pipe or tube N into which it is thrustlongitudinally, the leading-in wires being connected at one end of thepipe and insulated otherwise outside of the pipe. Since no foreignconducting articles can enter the sealed pipe and come in contact withwires K, it becomes safe to rely for insulation on the porcelains. Theaforesaid metal supporting strip A can slide along one of the internalsides of the pipe, while the rounded porcelain iianges E will slidealong the opposite interior face of the outside tube, as is shown inFig. 2. In other words,

. the rounded ribs E, the downwardly and inwardly tapered sides of thebases C, and the strip A are so relatively positioned and proportionedas to provide a heater of approximately circular.

'cross-section. ,This brings the wires K practically in the center ofthe tube when they are permanently maintained in position and the archeson the block give it, as stated above, a substantially circular contourtting the tubes. Moreover, this construction` permits theheat to beapplied in any direction by having the blocks turned towards any side ofthe tube where the heat is wanted. Then the faces of the blocks willactas reectors for the radiated' heat. I electrically connect succeedingsections,of conductor K, by short plates L which are held to the ends ofthe coiled wires K by a short bolt and nut. When it may be necessary 'toconnect the parallel wires K, I employ a U-shaped piece, M, shown inFig. 4, which bridges over the separator D and is screw-connected at itsrespective ends to the conductors K, K. The adjacent ends of theporcelain blocks may be secured to the metal support strip in anydesiredmanner, such as by bent fasteners, and on the bottom of each block areshort protuberances which serve to space the block from the strip. Thelongitudinal spacing of blocks from one another is to permit flexibilityof the series of blocks in order to follow bends in the metal strip. Theseparation of the blocks is normally slight but it may be greater atpoints where the sections o-f the metal strip are joined by splicing oroverlapping, or where the sections of the coiled conductors areconnected together.

, To illustrate the applicability of my construction to the purposesabove described, I have shown in Figs. 5 and 6 different types pf ajunction between two pipes containing heater coils placed at anangle toone another. In Fig. 5

an L-junction is shown and in Fig. 6 a T-junction. The junction occursat a break between adjacent blocks, and the conductors in the verticalline of blocks are connected to one or both of the conductors in thehorizontal line by metal connecting strips L. In practice the outsidemetal pipes may be placed in position first. Then the line ofstrip-supported blocks may be inserted and the conductors in thevertical set connected to the conductors ofthe horizontal set asmentioned above. Finally the couplings for the outside metallic tubesmay beapplied to seal the junction. The insulating blocks, lined upalong the metal strip` and attached thereto, are all joined up at thefactory and shipped in iinished lengths ready to be connected end to endwhen assembled on the ground. This assembling is, in my arrangement,even easier than the assembling of similar lengths'of cable.l So .far asI know, this is the first instance of a long length of flexibleconductor insulated by porcelainv blocks and ready to be inserted in ametal tube as contrasted with a cable insulated by a plastic covering;

Figs. 7, 8 and 9 exemplify typical uses of my invention for heating theedges of a gate in al dam. Such gates may be 75 feet high, or higher andexposed to the coldest winter weather. A slight leakage of water aroundthe edges is unavoidable and in winter the gate will, by freezing ofsuch leakage, become frozen fast in its frame so that it cannot be`raised or lowered, unless artificially heated. A

4In Fig. '7 R is the masonry of the dam and Sl is a gate set to slide invertical grooves in said masonry. Along the sides of the groove a spaceT is left for the insertion of my above-described heater. In said spaceare placed metal tubes for receiving the heater, these tubes may be atthe sides of the gate, as at the right of Fig. '7, or at the endthereof, as shown atthe left of Fig. 7 When these tubes are in place itonly remains to drop into them a length of my abovewhereas bysuspensionv from the top they hangA easily and safely.

In Figure 8, the tubular casing N` is provided at its upper end with anenlarged chamwith the longitudinal axis of saidv casing.

Said port is normally closed by a removable plug n3. A branch conduit n4is connected with the chamber n inA such manner that a conductor 115`may be brought to the chamber and connected in suitable manner witheach terminal ns located at the adjacent ends of theY resistors K.

In Fig. 9 the gate S is shown as also provided with marginal heating atits bottom edge. A pipe U extends down one side, carrying the lead wire`W. This pipe U communicates with a cross pipe Von the lower edge inwhich is placed a line of iny heater supplied by the wire or wires W.These pipes U and V rise and fall with the gate S. In such cases theactive face of the heater is turned to direct the heat in the desireddirection. Fig. 8 shows the suspension of a heater from its top'end inametal tube by means of the flexible strip A which is bent to hook on tothe top edge of the tube. The 'open end ofvtube V,

through which the unitary heater structure is insertable and removableis closed by a screw plug v'. The upper' end of pipe W is closed in asimilar manner by a plug w.

What I claim as new and desire to secure by Letters Patent is:

1. In an electric heater, means for supporting a heater element ofsubstantial length, said means comprising a at strip of flexiblematerial, a plurality of rigid blocks .of dielectric material arrangedadjacent each other and end for end in longitudinally spaced relationalong one fiat face of said strip, and means for i'lxedly attaching saidblocks to said strip in such manner that they are free to moverelatively to each other so as to conform,togilexib'le adjustments ofsaid strip, each of said blockshaving. means for engaging a heaterelement of a length approximately corresponding to the length of thestrip.

2. In an electric heater, means for supporting a heater elemen't ofsubstantial length, said means comprising a nat strip of exiblematerial, a plurality of blocks of dielectric material each having abase provided with an upper conductor receiving face for engaging aheater element of a length corresponding to the length of the strip.

'said blocks being arranged adjacent to each other end for end, and` inlongitudinally spaced relation along one flat face of said strip, and'means for xedly attaching said blocks to said strip lin such manner thatthey are free to\move relatively with respect to each other s0 as toconform to exible adjustments of said strip.

3. In an electric heater, means for supporting relation along saidstrip, and meansfor securing said blocks to said strips in such mannerthat the bottom faces of the blocks abut the adjacent face of the strip,and the blocks are free to move rality of rigid blocks of insulatingmaterial each having a base provided with an upper conductorreceivingface iand transversely disposed arched conductor-retaining membersextending from said upper face, said blocks being arranged adjacent toeach other in longitudinally spaced end for end relation along one :datface of said strip, means for flxedly attaching the bases of said blocksto said strip in such manner that they are free to move with respecttoeach other so as to conform to flexible adjustments of said strip, and alongitudinally disposed conductor of approximately the length vof thestrip extended throughthe arched members of successive insulator blocks.5. In an electric heater, means for supporting a heater element ofsubstantial length, said means comprising'a fiat strip of exiblematerial, a plurality of rigid blocks of dielectric material, eachprovided with a iiat base portion with conductorguide means on the topthereof, said blocks being arranged end for end adjacent to each otherand in longitudinally spaced relation along the strip with the bottomfaces of the base portions thereof in engagement with one at face ofsaid strip, and means for xedly attaching said blocks to said strip insuch manner that they are free to move with respect to' each other so asto con form to flexible adjustments of the strip.

6. In an electric heater, a exible strip, and

a plurality of rigid insulator blocks, each hav.- ing a base providedVwith an upper conductorreceiving face and having its lower portionattached to Asaid strip in a normally xed manner, saidconductor-receiving space having transversely disposed archedconductor-retaining members and a longitudinally disposed separatormember connecting said 'arched members, and longitudinally-disposedconductors disposed in -spaced relation along said separator members andextended through the arched members of successive insulator blocks, saidblocks being longitudinally spaced along said strip so as to be free toconform to flexible movement of the strip.

7. In an electric heater, a flat strip of e'xible material, a pluralityof rigid blocks of dielectric material arranged adjacent to each otherand inv end for end relation along one face of vsaid strip, each blockhaving a base portion positioned adjacent to said last mentioned face,means for ilxedlyL attaching the bases 0f said blocks to thev strip insuch manner that the blocks are free to move with respect to each otherto conform yto flexible adjustments of said strip, and one or moreconductors supported by said plurality of blocks, each conductorextending the full length of the series of said blocks.

8. In an electric heater, a ilat strip of! flexible material, a seriesof rigid blocks of dielectric material arranged adjacent to each otherand in end for end relation along one face of said strip, eachblock'being of greater length than its width and having its base portionengaging said last mentioned face, said base being'provided with aconductor-receiving portion, and means for fixedly attaching said blocksto said strip in such manner that the blocks are free to move withrespect to each other so as to conform to flexing adjustments of thestrip.

. 9. In an electric heater, means for supporting a heater elementofsubstantial length, said means comprising a flat stripv of exiblematerial, a series of rigid blocks. of dielectric material arrangedadjacent each other in end for end relation along one at face of saidstrip, each block having a base provided with a top portion from whichextend a plurality o f arched conductor-retaining members, and means forxedly attaching the bases of said blocks to said strip in such man-y nerthat they are f ree to move with respect to each other so as to conformto flexing adjustments of said strip, the faces of said blocks which lieadjacent to the strip having portions spaced from said strip.

10. In an electric heater,'means for supporting a heater element ofsubstantial length, said means comprising al flat strip of iiexiblematerial, a series of rigid blocks of dielectric material arrangedadjacent to each other in end for end longitudinallyspaced relationalong one face of the strip, each block having a base provided withv oneor more protuberances bearing against the said face of the strip, andmeans for attaching the blocks to said strip in such manner that theyare free to move with respect to eachother during flexing adjustments ofthe strip.

v11. In an electric heater, means for supporting a heater element ofsubstantial length, said means comprising a flat strip of flexiblematerial, a plurality of series ofrigid blocks of dielectric material,the blocks of each series being arranged adjacentto each other in endfor end relation along one face of the strip, any two series beingseparated by an intervening space between adjacent ends thereof, anelectric heater formed of sections corresponding approximately to thelength of a series of said' blocks, metal strips connecting adjacentends of the conductor sections across said intervening space, so as toprovide a continuous conductor extending the length of all of the seriesof blocks, and means for attaching the blocks to the strip in suchmanner that the blocks are free to move with respect to each otherduring flexing adjustments of said strip.

12. In an electric heater, means for supporting a heater element oflsubstantial length, said means comprising two or more at-strip-likesections of flexible material connected end for end to form a longerflat strip, a plurality of series of rigid blocks of dielectricmaterial, there being one series of said blocks for each section of saidstrip, each series of blocks being arranged with the blocks adjacenteach other in end for end relation and disposed along one face of astriplike section, the series being respectively spaced from each otherat the joints of the strip sections, and means for fixedly attaching theblocks to the strip sections in such manner that the blocks are movablewith respect to each other so as to conform with flexing adjustments ofthe longer strip.

13. In an. electric heater, a flexible strip, and a plurality of rigidinsulator blocks, each'block having a base attached to said strip, saidblocks being relatively spaced along said strip, so as to be freetoconform to flexible movements thereof, each block having alongitudinally disposed spacing rib on the top face thereof, conductorsengaging all of said blocks and disposed on either side of said ribs,and connectors between adjacent parallel conductors, each connectorconsisting of a metal strip shaped to pass over the said 'rib and havingits ends provided with conductor engaging means. l

14'. Inan electric heater, means for supporting a heater element ofAsubstantial length, said means comprising a fiat strip of flexiblematerial, a series of rigid blocks of dielectric material oi greaterlength than width, said blocks being arranged adjacentto each other inend for end relation and longitudinally spaced along one face of saidstrip, each block having a base provided with a at surface lyingadjacent to said face, and alsohaving arched conductor-engaging portionson theV face spaced outwardly from said flat surface, and means forfixedlyattaching said blocks to said strip in such manner that they arefree to move with respect to each other so as`to conform to flexingadjustments of said strip.

15. In an electric heater, a series of blocks of greater length thanwidth arranged end to end, a exible metallic strip located exteriorly ofthe blocks and ,attached thereto, each block having a flat base on theside next to the strip and transverselyA disposed longitudinally spacedarched projections on the face which is awal7 from said strip, saidprojections being provided with conductor-receiving openings, meansiixedly attaching the blocks to the strip, and conductors engaging thelast mentioned faces of said blocks and passed through said openings,said blocks being longitudinally spaced along said strip so as to befree to conform to exible movement thereof.

16. In an electric heater, a rigid insulator block having a base portionprovided on one face with an integral longitudinally disposed separatingrib and integral transversely disposed arch members extending above'theplane of said rib, Vsaid arch members having conductor-receivingopenings therein.

17. In an electric heater, a rigid insulator block having a base portionprovided on one face with an integral longitudinally disposed separatingrib and integral transversely disposed arch members extending above theplane of said rib, said arch members having conductor-receiving openingstherein, said base having inclined sides converging inwardly anddownwardly.

18. In an electricA heater, an elongated insulator block ofapproximately circular contour in cross section and having a at bottomsurface,

`a longitudinal rib on the top surface and arched portions extendingacross said rib and Yeach having a series of openings therein, theopenings in each arched portion-being equally spaced from.

the curved edges of said arched portion and also equally spaced withrespect to each other.

19,. An electric heater comprising a, tubular casing, and a-heaterelement within the casing,

said heater element including a exible metal strip and a series of rigidinsulator blocks, each block having a contour complemental tosaid tube,said blocks being attached to said strip in longitudinally spacedrelation, so as to conform to flexible movement thereof, said stripbeing necting said blocks in a longitudinal series-at and arranged toengage an end of the casing tov suspend'` said heater element therein.

22. An electric heater comprisingV a tubular casing, and a heaterelement within said casing, y

said heater element including a .series of rigid necting said blocks ina longitudinal series at positions outside of the mocks, anafmaintamingthem in exible longitudinally spaced relation, and electric conductorsextending the length of the series and engaging said insulator blocks.

. ing, a continuous ilexible m'etal support member extending.longitudinally within said casing, a series of insulator blocks locatedwithin said casing and each provided on Cone side with archedprojections complemental to the interior of the tube, and having theother side attached to said support, and continuous electricalconductors extended through said arched projections.

24. In an electric heater, two connected tubular casings disposed at anangle with respect to each other, each of said `casings containingheater elements each including a series of insulator blocks each havinga base portion attached to a exible strip extended longitudinallythrough its casing, said blocks being longitudinally spaced so as toconform to ilexible movements of said strips, electric conductorssupported by the respective series of insulator blocks, and meansestablishing'electrical connection between the conductors in therespective casings.

25.` In an electric heater, a ilatstrip of flexible material, aplurality of rigid blocks of dielectric material arranged adjacent toeach other in end for end relation and longitudinally spaced along onefiat face of said strip, each of said blocks having a plurality dfangularly disposed conductor-supportingfaces so constructed and ar'casing, heating means within said casing, said heating means comprisinga at strip of iiexible material extended longitudinally through thetube, a plurality of rigid blocks of dielectric material arrangedadjacent to each other in end for end relation and relatively spacedlongitudinally along one face ofsaid strip, each block having across-sectional contour complemental to the cross-sectional contour ofsaid casing, means for ilxedly attaching said blocks to said strip insuch manner that the blocks are freeto move 'with respect to each otherso as to conform to ilexing adjustments of said strip, electricalheating elements carried by said blocks, and means on said blocks formaintaining said heater elements inv respect to the wall oi' the andremoved vfrom said casing, and exposed electrical conductors extendingthroughout the length of the casing and supported by all of the blocks.

28. An electric heater comprising an external casing, a series ofinsulator blocks therein, a 23. In an electric heater, a tubular metalcasilexible strip attached to said blocks and passing between the blocksand the interior surface of the casing, said strip being formed of twoor more sections connected end for end, electrical conductors engagingsaid blocks and each formed of two or more sections joined end for end,said blocks being normally spaced approximately uni- -form distancesfrom each other, but more Widely bodiesand provided with spaced openingspositioned and arranged to correspondingly space electric resistor coils in front of said reflecting walls, means in said downwardlyextended open- I ings constructed and arranged to secure the blocks tosupport means, and means carried by said blocks for interconnecting twoor more resistor coils.

30. In an electric heater, a plurality of aligned insulator blocks eachprovided with a middle longitudinally disposedreenforcing rib and heatreflecting walls arranged in different planes,

transversely disposed cross members projecting upwardly from said bodiesand provided with relatively spaced openings positioned and arranged tocorrespondingly space electric resistor coils in front of saidreflecting Walls,` support means, and attaching means extendeddownwardly through the rib of each block. and releasably engaging saidsupport means at a position below the block.

31. In an electric heater, a casing having a terminal chamber, aplurality of aligned insulator blocks each provided with a middlelongitudinally disposed reenforcing rib and heat reiiecting wallsarranged in the casing in different planes, each block having openingsextended downwardly therethrough from the tops of said ribs,transversely disposed cross members projecting upwardly from said bodiesand provided with spaced openings positioned and arranged tocorrespondingly space electric resistor coils in front of saidreflecting walls, a iiexible support, meansin the openings through saidblocks constructed and arranged to connect said blocks with said supportmember, and means carried by said blocks for interconnecting two or moreresistor coils.

32. In an electric heater, a rigid insulator block having one yfaceprovided with an integral longitudinally disposed separator rib an'dintegral transversely disposed spacer members extending above the planeof said rib, said transverse members having conductor-receiving openingstherein so arranged as to space electric conductors Awith relation tothe faces of the rib, and means extended over said rib and provided withportions constructed and arranged to interconnect said conductors at oneend.

33.In a heater of the character described, the combination with atubular casing adapted to be supported adiacent to an object havingf anarea to be heated, of heating means insertable into and removable from'said casing while the latter is in a xed position, said heating meanscomprising a at strip of flexible material extended longitudinallythrough the tube, a plurality o! rigid blocks of dielectric materialarranged adjacent to each other in end for endrelation and relativelyspaced longitudinally along one face of said strip,`means for xedlyattaching the blocks to said strip in such manner that said blocks arefree to move with respect to each other so as to conform to flexingadjustments of the strip, electrical heating elements carried by saidblocks, and

.means on said blocks for maintaining said heater elements in spacedrelation with respect to the wall of the casing.

34. In a heater of the character described, the combination'with aiiexible tubular casing, of heating means insertableinto and removablefrom said casing, said heating means comprising a at strip of exiblematerial extended longitudinally through said casing, a plurality ofrigid blocks of dielectric material arranged adjacent to each other inend vfor end relation and secured vthey are free to mQvewith respect toeach other to conform to flexing adjustments of said strip as it isinserted into and removed from said casing, and electrical heatingelements carried by said blocks.

35. In aheater of the character described, thecombination with a bodyhaving an area to be heated, said bodyhaving a longitudinal groovetherein contiguous to said area, of a tubular casing located Within saidgroove, and heating means insertable into and removable from said casingwhile the latter is in operative position, said heating means comprisinga at strip of exble mataching said blocks to the strip in such'mannerthat the blocks are free to move with respect to each other so as toconform to flexing adjustments of the strip, and electrical heatingelements carried by said blocks.

36. In a heater of the character described, the combination with atubular casing adapted to be supported adjacent to an object having anarea to be heated, of heating means insertable into and removable fromsaid casing while the latter is in operative position, said heatingmeans comprising a iiatI strip of exible material extendedlongitudinally through the tube, a plurality of rigid blocks ofdielectric material arranged adiacent each other in end for end relationand relatively spaced longitudinally along one facev of said strip, eachblock having a cross sectional contour complemental to the crosssectional contour of the casing, means for xedly attaching said blocksto said strip in such manner that the blocks are free to move withrespect to each other so as to conform to ilexing adiustments of thestrip, electrical heating means carried by said blocks, and means onsaid blocks for maintaining said heaterl elements in\spaced relationwith respectv to the wall of the casing, said heating means beingrotatively adjustable within the casing so as to bringl the heatingelements adjacent to the area to be heated.

37. An electric heater comprising a tubular casing having an enlargedchamber at one end, said chamber having a port therein in alignment withthe casing, a branch conduit for electrical conductors, said conduitcommunicating with said chamber, a unitary heater structure -consistingof a ilat strip of flexible material, a plurality of insulator blocksattached to said strip and arranged in spaced relation along one side ofthe strip and one or more heater elements engaging and supported by allof the blocks in such manner that said elements are spaced from the wallof the casing, said strip and said heater elements beingof approximatelythe same length as the casing, said unitary structure being soconstructed and arranged that it may be introduced -into the casing andremoved therefrom through said opening-as a unit, a closure for saidport, means for so restricting longitudinal movement of vsaid unitaryheater structure as to maintain an end of each heater element withinsaid chamber, and means within the chamber whereby the heater elementsmay be connected with a conductor carried by said branch conduit.

' -LEE P. HYNES.

